Fasciculation is spontaneous, brief twitches of the muscle fibers within a motor unit that occur when the muscle is at rest. These twitches are visible under the skin as a fine, rapid ripple but do not cause actual movement of the limb because they are small and unsynchronized. This distinguishes fasciculations from other movement problems: dystonia involves sustained or repetitive muscle contractions that produce abnormal postures; athetosis features slow, writhing movements; chorea consists of quick, irregular jerks that flow from one muscle group to another. There’s also fibrillation, a related but subtler phenomenon detected by EMG, where individual muscle fibers contract spontaneously and are not visible clinically. So the description of rapid, continuous twitching of a resting muscle without movement best fits fasciculations.